Procedures for preparing photographic images in silver by diffusion transfer principles are well known in the art. For the formation of the positive silver images, a photosensitive silver halide emulsion is exposed and contacted with a processing composition containing a silver halide solvent so that a latent image contained in the exposed emulsion is developed and, almost concurrently therewith, a soluble silver complex is obtained by reaction of the silver halide solvent with the unexposed and undeveloped silver halide of said emulsion.
This soluble silver complex is, at least in part, transported in the direction of a print-receiving element and the silver thereof is largely precipitated in the silver precipitating element to form a positive image thereon. Preferably, the photosensitive silver halide emulsion is developed with a processing composition which is spread between the photosensitive element comprising the silver halide emulsion and a print-receiving element comprising a suitable silver-precipitating layer. Procedures of this description are disclosed, for example in U.S. Pat. No. 2,543,181 issued to Edwin H. Land. See, also, Edwin H. Land, One Step Photography, Photographic Journal, Section A, pp. 7-15, January 1950.
Additive color reproduction may be produced by exposing a photosensitive silver halide emulsion through an additive color screen having filter media or screen elements each of an individual additive color, such as red or green or blue, and by viewing the reversed or positive silver image formed by transfer to a transparent print-receiving element through the same or a similar screen which is suitably registered with the reversed or positive image carried by the print-receiving layer.
As examples of suitable film structures for employment in additive color photography, mention may be made of U.S. Pat. Nos. 2,861,885; 2,726,154; 2,944,894; 3,536,488; 3,615,427; 3,615,428; 3,615,429; 3,615,426; and 3,894,871.
Such film assemblies as those disclosed in the above indicated patents find particular utility in cine film systems such as, for example, the system described in U.S. Pat. No. 3,615,127 which includes a compact film cassette or container adapted to allow exposure of a film assemblage retained therein, subsequent processing of the film unit to provide the desired image record and projection of the resultant image record. Thus, the film assemblage may be exposed, processed, and projected without transferring the film from its original container. The cine film system of U.S. Pat. No. 3,615,127 includes a film processing station whereupon the exposed film strip is transported from a first storage reel, past an applicator where a moist processing composition adapted to develop to a visible condition images recorded on the film is applied and thence to a second storage reel.
The additive diffusion transfer film units disclosed above are processed by an aqueous alkaline processing composition adapted to effect development of the latent image in the silver halide emulsion and provide a positive silver image thereby, and which preferably includes a silver halide developing agent and a silver halide solvent.
Silver halide solvents useful in forming the desired soluble complex with unexposed silver are well known and, for example, may be selected from the alkali metal thiosulfates, particularly sodium or potassium thiosulfates, or the silver halide solvent may be a cyclic imide, such as uracil, in combination with a nitrogenous base as taught in U.S. Pat. No. 2,857,274 issued Oct. 21, 1975, to Edwin H. Land or a pseudo uracil, such as the 4,6-dihydroxypyrimidines as taught in U.S. Pat. No. 4,126,459, issued Nov. 21, 1978.
The processing composition may contain a thickening agent, such as an alkali metal carboxymethyl cellulose or hydroxyethyl cellulose, in a quantity and viscosity grade adapted to facilitate application of the processing composition. The processing composition may be left on the processed film or removed, in accordance with known techniques, as is most appropriate for the particular film use. The requisite alkalinity, e.g., a pH of 12-14, is preferably imparted to the processing composition, by an alkaline material, such as sodium, potassium and/or lithium hydroxide.
Suitable silver halide developing agents may be selected from amongst those known in the art, and may be initially positioned in a layer of the photosensitive element and/or in the processing composition. Organic silver halide developing agents are generally used, e.g., organic compounds of the benzene or naphthalene series containing hydroxyl and/or amino groups in the para- or ortho- positions with respect to each other, such as hydroquinone, tert-butyl hydroquinone, toluhydroquinone, p-aminophenol, 2,6-dimethyl-4-aminophenol, 2,4,6-triaminophenol, etc. Particularly useful silver halide developing agents having good stability in alkaline solution are substituted reductic acids, particularly tetramethyl reductic acid, as disclosed in U.S. Pat. No. 3,615,440 issued Oct. 26, 1971 to Stanley M. Bloom and Richard D. Cramer, and .alpha., .beta.-enediols as disclosed in U.S. Pat. No. 3,730,716 issued to Edwin H. Land, Stanley M. Bloom and Leonard C. Farney on May 1, 1973.
U.S. Pat. No. 3,782,263 discloses a motion picture film which carries a pair of elongated rail-like protuberances which are carried on the opposite side of the film strip from the photosensitive silver halide emulsion. These protuberances preferably project above the surface of the film unit a distance exceeding the height of deposited fluid processing composition. When the motion picture film is rewound subsequent to the application of the processing composition, the processing composition is not in a completely dried state and the above-described protuberances provide means for spacing adjacent turns of the film strip and thus prevent adhesion of such turns and subsequent damage to the film upon unwinding
By means of the present invention, it has now been found that the problem of film adhesion can be alleviated or eliminated entirely without the use of the above-mentioned rail-like protuberances.